<!DOCTYPE html>
<html>

<head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>3.姓名案例_watch实现</title>
    <!-- 引入Vue -->
    <script type="text/javascript" src="../js/vue.js"></script>
</head>

<body>
    <!-- 准备好一个容器-->
    <div id="demo">
        姓:<input type="text" v-model="firstName"></br>
        名:<input type="text" v-model="lastName"></br>
        全名:<span>{{fullName}}</span>
    </div>
</body>

<script type="text/javascript">
    //阻止 vue 在启动时生成生产提示。
    Vue.config.productionTip = false
    new Vue({
        el: '#demo',
        data: {
            firstName: 'zhang',
            lastName: 'san',
            fullName:''
        },
        //采用watch监听数据变化
        watch: {
                firstName: {
                immediate:true,//立即监视必须写在需要监视的已经存在的对象内部
                handler(val) {
                    this.fullName = val + '-' + this.lastName
                }
            },
            //监听lastname(名)
            lastName:{
                handler(val){
                    this.fullName = this.firstName +'-'+ val
                }
            }
        }
    })
</script>

</html>